The Fluke Calibration 5608 is a high-precision secondary reference platinum resistance thermometer (PRT) designed for accurate and reliable temperature measurements in calibration laboratories, industrial environments and temperature metrology applications.
With a temperature range from −200 °C to +500 °C, a slim Inconel sheath and excellent short-term stability, the Fluke Calibration 5608 provides a professional solution for temperature comparison calibration, reference temperature measurements and the verification of industrial temperature sensors.
The thermometer features a high-quality platinum resistance sensing element with a four-wire connection, minimizing the influence of connecting lead resistance on measurement results.
One of the most important advantages of the Fluke Calibration 5608 is its small sheath diameter of only 3.18 mm (1/8 inch). This slim design reduces stem conduction effects and allows accurate temperature measurements at relatively shallow immersion depths.
The manufacturer specifies a minimum immersion depth of 80 mm, making the Fluke Calibration 5608 particularly suitable for applications where available immersion depth is limited.
Two probe lengths are available: 228.6 mm and 304.8 mm.
The Fluke Calibration 5608 is supplied with an individually measured resistance value at the triple point of water. An accredited calibration with ITS-90 coefficients can be ordered separately.
When combined with a suitable precision thermometer readout, the Fluke Calibration 5608 provides a versatile reference temperature measurement system.
At europascal, the Fluke Calibration 5608 is an excellent choice for professional temperature calibration and reference measurement applications.
For professional calibration services and metrological traceability, visit the europascal Calibration Service.
Your Benefits at a Glance
- High-precision secondary reference thermometer
- Temperature range from −200 °C to +500 °C
- Platinum resistance sensing element
- Excellent short-term stability of ±0.01 °C
- Slim 3.18 mm probe diameter
- Minimum immersion depth of 80 mm
- Available in two probe lengths
- High-quality Inconel sheath
- Four-wire resistance measurement
- Reduced influence of connecting lead resistance
- Suitable for temperature comparison calibration
- Suitable for calibration baths and dry-block calibrators
- Individual resistance value at the triple point of water
- Optional accredited calibration
- Optional ITS-90 calibration coefficients
- Different connector configurations
- Compatible with suitable Fluke Calibration thermometer readouts
- Professional calibration support from europascal
Precision Temperature Measurement from −200 °C to +500 °C
The Fluke Calibration 5608 provides accurate temperature measurements over a wide operating range.
Temperature range: −200 °C to +500 °C
This range covers cryogenic applications, low-temperature calibration, ambient temperature measurements and elevated-temperature industrial applications.
The thermometer can be used in suitable liquid calibration baths, dry-block calibrators and other temperature-controlled environments.
Its precision platinum resistance element provides stable and reproducible resistance measurements.
For accurate temperature indication, the probe must be connected to a compatible precision thermometer readout.
The complete measurement uncertainty depends on the probe calibration, readout performance and measurement conditions.
Secondary Reference Platinum Resistance Thermometer
The Fluke Calibration 5608 is classified as a secondary reference platinum resistance thermometer.
Secondary reference thermometers are used in calibration laboratories to transfer temperature values from higher-level reference standards to working thermometers and industrial sensors.
The Fluke Calibration 5608 is particularly suitable for temperature comparison calibration.
A calibrated reference thermometer and a temperature sensor under test are placed in a stable temperature source.
The difference between the indicated temperatures can then be evaluated.
This method is widely used for the calibration of industrial Pt100 sensors, resistance thermometers and temperature measurement systems.
High-Quality Platinum Resistance Element
The Fluke Calibration 5608 uses a precision platinum resistance sensing element.
Platinum is widely used in reference temperature measurement because of its reproducible resistance-temperature relationship and good long-term stability.
The electrical resistance of the sensing element changes with temperature.
A compatible thermometer readout measures this resistance and converts it into temperature using the selected calibration characteristic.
For high-accuracy measurements, the resistance-temperature relationship can be determined through calibration.
The resulting calibration coefficients allow the thermometer readout to calculate temperature according to the characteristics of the individual probe.
Excellent Short-Term Stability
Temperature stability is an important characteristic of reference thermometers.
The manufacturer specifies short-term stability of:
±0.01 °C
This value demonstrates the excellent reproducibility of the Fluke Calibration 5608 under the manufacturer’s defined test conditions.
Short-term stability is particularly important when the thermometer is repeatedly used at different calibration temperatures.
A stable reference thermometer helps reduce uncertainty contributions associated with changes in sensor characteristics.
However, short-term stability should not be confused with absolute measurement accuracy.
The actual accuracy of the thermometer depends on its calibration and the connected readout.
Slim 3.18 mm Probe Diameter
One of the most important design features of the Fluke Calibration 5608 is its slim probe sheath.
Sheath diameter: 3.18 mm
The small diameter provides several advantages.
It allows the probe to fit into narrow calibration inserts and measurement openings.
It also reduces the influence of heat conduction along the probe stem.
This is particularly useful when measuring temperatures in environments where only limited immersion depth is available.
The slim design can also improve thermal response compared with larger-diameter probes under similar measurement conditions.
Minimum Immersion Depth of 80 mm
The Fluke Calibration 5608 has a manufacturer-specified minimum immersion depth of:
80 mm
Immersion depth is particularly important in precision temperature measurements.
If a thermometer is not immersed sufficiently, heat can be conducted along the probe stem between the measurement environment and the surrounding air.
This effect is commonly known as stem conduction or stem effect.
The resulting temperature difference can introduce measurement errors.
The slim design of the Fluke Calibration 5608 helps reduce this effect.
For demanding calibration applications, the required immersion depth should nevertheless be verified under the actual measurement conditions.
High-Quality Inconel Sheath
The Fluke Calibration 5608 features a high-quality Inconel sheath.
Inconel is a nickel-based alloy known for its mechanical strength and resistance to elevated temperatures.
The sheath protects the precision platinum sensing element.
It also provides mechanical durability during repeated use in calibration laboratories.
The material is suitable for many temperature calibration applications involving controlled temperature sources.
Chemical compatibility should be considered when the probe is exposed to aggressive measurement media.
Four-Wire Resistance Measurement
The Fluke Calibration 5608 uses a four-wire connection.
Four-wire resistance measurement is particularly important for precision temperature measurement.
In a conventional two-wire connection, the resistance of the connecting leads contributes to the measured resistance.
This can introduce significant errors when measuring a platinum resistance thermometer.
A four-wire connection separates the current-carrying conductors from the voltage-sensing conductors.
This minimizes the influence of lead resistance.
The result is a more accurate determination of the sensing element resistance.
Calibration at the Triple Point of Water
The Fluke Calibration 5608 is supplied with an individually measured resistance value at the triple point of water.
The triple point of water corresponds to:
0.01 °C
This temperature is an important reference point in temperature metrology.
The resistance measured at the triple point provides information about the characteristics of the platinum sensing element.
It can also be used as a reference value when evaluating the stability of the thermometer.
The standard resistance measurement does not replace a complete multipoint calibration.
For high-accuracy temperature measurements, an appropriate calibration over the required temperature range is recommended.
Optional Accredited Calibration
The Fluke Calibration 5608 can be ordered with an accredited calibration.
Fluke Calibration offers calibration services for secondary reference thermometers.
An accredited calibration provides documented measurement results and supports metrological traceability.
Depending on the selected calibration service, the calibration certificate includes measured values and ITS-90 coefficients.
These coefficients can be entered into a compatible thermometer readout.
This allows the individual resistance-temperature characteristic of the probe to be used for temperature calculation.
Accredited calibration is optional and is not included automatically with the standard probe.
ITS-90 Temperature Conversion
The International Temperature Scale of 1990, commonly known as ITS-90, is widely used in precision temperature metrology.
A calibrated platinum resistance thermometer can be characterized using ITS-90 calibration coefficients.
These coefficients describe the relationship between the resistance of the thermometer and temperature.
When the Fluke Calibration 5608 is supplied with an appropriate calibration, the coefficients can be entered into a compatible thermometer readout.
This allows temperature to be calculated according to the individual characteristics of the probe.
For the highest measurement accuracy, the thermometer should be used with its own calibration coefficients.
Intelligent Sensor Connectors
The Fluke Calibration 5608 is available with different connector options.
Compatible INFO-CON connectors can store calibration coefficients and probe information.
When the probe is connected to a compatible Fluke Calibration thermometer readout, the stored coefficients can be retrieved automatically.
This simplifies the configuration of the measurement system.
It also reduces the risk of errors caused by incorrect manual entry of calibration coefficients.
The availability of this function depends on the selected connector and thermometer readout.
Available Probe Lengths
The Fluke Calibration 5608 is available in two versions.
Fluke Calibration 5608-9-X
Probe length: 228.6 mm (9 inches)
Probe diameter: 3.18 mm (1/8 inch)
Temperature range: −200 °C to +500 °C
This version is suitable for compact calibration setups and applications requiring a shorter reference thermometer.
Fluke Calibration 5608-12-X
Probe length: 304.8 mm (12 inches)
Probe diameter: 3.18 mm (1/8 inch)
Temperature range: −200 °C to +500 °C
This version provides additional length for applications requiring deeper immersion.
Both versions feature the same nominal sheath diameter and temperature range.
Available Connector Configurations
The Fluke Calibration 5608 can be supplied with different electrical connections.
| Connector Code | Connection Type |
|---|---|
| A | INFO-CON for Fluke 914X |
| B | Bare wire |
| D | 5-pin DIN |
| G | Gold pins |
| J | Banana plugs |
| L | Mini spade lugs |
| M | Mini banana plugs |
| P | INFO-CON for Fluke 1523/1524 |
| S | Spade lugs |
The appropriate connector should be selected according to the thermometer readout.
Compatible Thermometer Readouts
The Fluke Calibration 5608 is a passive platinum resistance thermometer.
It does not include an integrated display.
A suitable thermometer readout is required to measure resistance and calculate temperature.
Depending on the selected connector, the Fluke Calibration 5608 can be used with compatible instruments such as:
- Fluke Calibration 1523
- Fluke Calibration 1524
- Fluke Calibration 1529
- Fluke Calibration 1502A
- Other compatible precision resistance thermometer readouts
The electrical connection and supported sensor characteristics must be checked before use.
Temperature Comparison Calibration
The Fluke Calibration 5608 is particularly suitable for temperature comparison calibration.
A calibrated reference thermometer is placed in a stable temperature source together with the sensor under test.
Both temperature indications are recorded.
The indication error is calculated as:
ΔT = T_DUT − T_REF
Where:
- ΔT = Temperature indication error
- T_DUT = Temperature indicated by the device under test
- T_REF = Reference temperature
This method is commonly used in professional temperature calibration laboratories.
The measurement uncertainty must consider the reference thermometer, thermometer readout, temperature source and measurement conditions.
Calibration Baths
The Fluke Calibration 5608 is suitable for use in compatible liquid calibration baths.
Liquid calibration baths provide stable and relatively uniform temperature conditions.
A calibrated reference thermometer can be immersed together with one or more temperature sensors under test.
The Fluke Calibration 5608 measures the reference temperature.
This allows the indication errors of the sensors under test to be determined.
The slim sheath provides flexibility when positioning the probe inside the calibration bath.
Dry-Block Temperature Calibration
The Fluke Calibration 5608 can also be used with dry-block temperature calibrators.
A suitable calibration insert provides a measurement opening for the reference thermometer.
The reference probe is inserted into the dry-block calibrator.
The temperature of the reference probe is measured using a compatible thermometer readout.
This allows the actual temperature to be compared with the indication of the device under test.
The minimum immersion depth and thermal conditions must be considered.
Temperature Stability Measurements
Temperature stability is an important characteristic of calibration baths and dry-block calibrators.
The Fluke Calibration 5608 can be used to monitor temperature fluctuations over time.
When connected to a suitable thermometer readout or data acquisition system, the probe provides accurate resistance measurements.
These measurements can be converted into temperature and recorded.
The resulting data can be used to evaluate the stability of the temperature source.
This is particularly useful for laboratory equipment verification and calibration system characterization.
Technical Highlights
| Feature | Fluke Calibration 5608 |
|---|---|
| Product type | Secondary Reference Platinum Resistance Thermometer |
| Manufacturer | Fluke Calibration |
| Temperature range | −200 °C to +500 °C |
| Sensor type | Precision Platinum Resistance Thermometer |
| Short-term stability | ±0.01 °C |
| Sheath diameter | 3.18 mm |
| Available probe lengths | 228.6 mm / 304.8 mm |
| Minimum immersion depth | 80 mm |
| Sheath material | Inconel |
| Electrical connection | Four-wire |
| Lead-wire length | Approximately 1.83 m |
| Triple-point resistance value | Supplied individually |
| Accredited calibration | Optional |
| ITS-90 coefficients | With appropriate calibration option |
| INFO-CON connector | Optional |
| Compatible readouts | Depending on connector |
| Integrated display | No |
| Temperature generation | No |
Fluke Calibration 5608 vs. Fluke Calibration 5609
The Fluke Calibration 5608 and 5609 belong to the same secondary reference thermometer series.
Both instruments feature precision platinum sensing elements, Inconel sheaths and four-wire connections.
The main differences are temperature range, probe diameter and available lengths.
| Feature | Fluke Calibration 5608 | Fluke Calibration 5609 |
|---|---|---|
| Temperature range | −200 °C to +500 °C | −200 °C to +670 °C |
| Sheath diameter | 3.18 mm | 6.35 mm or 6 mm |
| Minimum immersion depth | 80 mm | 100 mm |
| Short-term stability | ±0.01 °C | ±0.01 °C |
| Sheath material | Inconel | Inconel |
| Four-wire connection | Yes | Yes |
| Accredited calibration | Optional | Optional |
The Fluke Calibration 5608 is particularly suitable for applications requiring a slim reference thermometer.
The Fluke Calibration 5609 is designed for applications requiring higher maximum temperatures.
Typical Applications
The Fluke Calibration 5608 is suitable for:
- Secondary reference temperature measurements
- Temperature calibration laboratories
- Platinum resistance thermometer calibration
- Pt100 calibration
- Temperature comparison calibration
- Liquid calibration baths
- Dry-block temperature calibration
- Temperature stability measurements
- Temperature uniformity measurements
- Industrial temperature sensor verification
- Reference temperature measurement
- Quality assurance
- Research laboratories
- Temperature metrology
- Laboratory temperature calibration
Calibration by europascal
Regular calibration is essential for maintaining reliable temperature measurement results.
europascal provides professional calibration services for temperature measuring instruments and reference temperature measurement systems.
The Fluke Calibration 5608 can be calibrated to determine its resistance-temperature characteristic.
An appropriate calibration provides measurement results that can be used to calculate individual calibration coefficients.
When combined with a compatible precision thermometer readout, the probe forms a reference temperature measurement system.
The overall measurement uncertainty depends on the probe calibration, readout accuracy, sensor stability and measurement conditions.
For professional calibration and metrological traceability, visit the europascal Calibration Service.
europascal also supports customers with the selection of suitable reference thermometers and temperature calibration equipment.
Why Choose the Fluke Calibration 5608?
The Fluke Calibration 5608 combines excellent temperature stability, a wide measurement range and a slim probe design in one professional secondary reference thermometer.
Its temperature range from −200 °C to +500 °C covers a wide variety of laboratory and industrial calibration applications.
The slim 3.18 mm sheath reduces the influence of stem conduction and allows measurements with relatively shallow immersion.
The manufacturer specifies a minimum immersion depth of 80 mm.
The high-quality Inconel sheath provides mechanical durability.
Four-wire resistance measurement minimizes errors caused by connecting lead resistance.
Optional accredited calibration and ITS-90 coefficients allow the thermometer to be used as part of a traceable reference temperature measurement system.
Different probe lengths and connector options provide flexibility for different applications.
For professional users requiring a precise and stable secondary reference thermometer, the Fluke Calibration 5608 provides an excellent combination of performance, reliability and versatility.
europascal supports customers with reference temperature probes, temperature calibration equipment and professional calibration services.
